This Week in Space: Metal on Mars, Hydrogen Inside Enceladus, and a Meteoric Near-Miss

We didn’t get pasted by that asteroid that sailed through Wednesday, which is arguably a good thing. Discovered in 2014, it was due to pass by Earth at a close but safe distance, which it won’t do again for another 500 years. Scientists all over the world took the opportunity to make a number of radar and other observations of the asteroid, so soon we’ll have some data on its structure and properties.

While we’re talking about icy rocks from the outer Solar System, it would be a shame not to mention Enceladus. This week scientists have been discussing the hydrogen efflux from the frozen moon. Hydrogen gas bubbling up from the depths of Enceladus’ frozen ocean leads scientists to the conclusion that Enceladus, like Earth, has deep ocean vents bubbling hydrogen through the briny waters. But unlike Earth, there’s a surprising volume of hydrogen coming out of those vents and floating off into space. This is bad news for fans of the idea that there’s currently extraterrestrial life on Enceladus: the fact that there’s so much ambient hydrogen suggests that there’s nothing on Enceladus currently using it.

Closer to Earth, scientists provided a goldmine of scientific puns with the revelation that the atmosphere of Mars is full of metal. Already named after a god of war, all it needs now is a lead guitarist. If we haven’t lost you already due to lethal brainhurt from that terrible play on words, head on over and check out what the scientists found.

The most recent beauty shot from the European Southern Observatory in Chile celebrates the Hubble Space Telescope’s 27th year in orbit with a portrait of two close friends: a pair of spiral galaxies, one turned edge-on while the other faces the telescope.

This image displays the galaxies NGC 4302 — seen edge-on — and NGC 4298, both located 55 million light-years away. They were observed by Hubble to celebrate its 27th year in orbit. The galaxy NGC 4298 is seen almost face-on, allowing us to see its spiral arms and the blue patches of ongoing star formation and young stars. In the edge-on disc of NGC 4302 huge swathes of dust are responsible for the mottled brown patterns, but a burst of blue to the left side of the galaxy indicates a region of extremely vigorous star formation. Captured by Hubble’s Wide Field Camera 3. Image and caption: ESO

Dark matter pervades the large-scale structure of the universe. Now researchers have used gravitational lensing to make the clearest, finest-grained image yet of the way dark matter is distributed in intergalactic space. Filaments of dark matter trail between galaxies, stringing them together like beads. A multi-year sky survey of more than 23,000 deep-sky galaxy pairs has yielded a highly detailed portrait of gravitational lensing. The way that lensing distorts the path of photons is our current best imaging technique, and that’s as close to directly imaging dark matter as we’ve come.

Image: Royal Astronomical Society / Hudson and Epps, 2017

“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” said Mike Hudson, a professor of astronomy at the University of Waterloo. “This image moves us beyond predictions to something we can see and measure.” Hudson and coauthor Seth Epps report their findings in the Monthly Notices of the Royal Astronomical Society.